The present invention relates to a DC motor torque controller. More particularly, the invention relates to a aircraft DC starter-generator torque controller in aircraft power transfer apparatus between auxiliary equipment such as, for example, aircraft starter-generator and a turbine engine through the gearbox of the turbine engine.
Heretofore, the starter-generator placed on board aircraft was sized to just meet the basic electrical needs of the aircraft with a safety factor. Size was kept to a minimum to keep the weight as low as possible to enable more lifting power to be utilized for fuel and load considerations which also affect range of flight. As more demands were put on the electrical power system with added gear, the onboard DC generator needed to be upgraded to handle the loads. Since the generator is also used for starting the engine, the resultant torque capability of the starter portion of the larger amperage starter-generator approached or exceeded the maximum rating of the gearbox and could not be safely operated during the start-up procedure. Thus, while the electrical loads could be safely operated during steady state conditions, the starter motor portion of the generator could not operate safely during the start-up procedure.
Changing the gearbox for the higher torque rating would be a severe setback, since it would require redesign of the engine gear box, which would result in added weight and prohibitive cost to retrofit existing aircraft or new aircraft using this same engine.
The principal object of the invention is to provide a aircraft DC starter-generator torque controller which reduces the very high initial starting torque of a DC shunt motor (starter-generator) used in the starting cycle of an aircraft turbine engine.
An object of the invention is to provide a DC motor torque controller which reduces the very high initial starting torque of a DC shunt motor used in the starting cycle of an aircraft turbine engine and maintains a controlled torque level during engine run-up to operating speed.
Another object of the invention is to provide a DC motor torque controller which reduces the very high initial starting torque of a DC shunt motor used in the starting cycle of an aircraft turbine engine, maintains a controlled torque level during engine run-up to operating speed, permits shorter time to engine lite off and lower engine temperature, permits setting of the rate of reduction of pulse width modulation (PWM) duty cycle and permits automatic switchover point for field control from terminal voltage control to armature current control for field weakening and increasing motor speed.
Still another object of the invention is to provide a aircraft DC starter-generator torque controller which permits higher rated startergenerators to permit increases in electric power available for use, which can satisfy extra load requirements and still remain within limitations imposed by the torque ratings of the power transfer gearbox.
Yet another object of the invention is to provide a aircraft DC starter-generator torque controller which controls or regulates the developed torque of a DC shunt motor, which may permit higher rated parts to be used on existing or future-designed equipment, one application of such controller being for an engine starter motor generator wherein the motor-generator is used for engine starting, after which the engine is utilized to drive the motor-generator to generate DC power.
Another object of the invention is to provide a aircraft DC starter-generator torque controller which lowers the maximum developed peak torque of a DC shunt motor during initial start-up from zero speed.
Still another object of the invention is to provide a aircraft DC starter-generator torque controller which maintains the developed torque of a DC shunt motor at a controlled higher level for a longer period of time during engine run-up to operating speed, thereby insuring the functioning of utilization equipment as intended.
Yet another object of the invention is to provide a aircraft DC starter-generator torque controller which permits higher rated DC shunt startergenerators to be used in applications where maximum torque excursions are limited by power transfer equipment.
Another object of the invention is to provide a aircraft DC starter-generator torque controller which permits the selection of the motor terminal voltage at which the torque control and/or regulating operation is initiated.
Still another object of the invention is to provide a aircraft DC starter-generator torque controller which permits a determination of the rate of reduction of torque control with terminal voltage.
Yet another object of the invention is to provide a aircraft DC starter-generator torque controller which permits a determination of the automatic switchover point for field control from terminal voltage control to armature current closed loop field weakening control.
Yet another object of the invention is to provide a DC generator torque controller which permits higher rated motor-generators to permit increases in electric power available for use, which can satisfy extra load requirements and still remain within limitations imposed by the torque ratings of the power transfer gearbox.